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Thread: CFL flicker with switch off

  1. #1
    Join Date
    Sep 2005
    Posts
    17

    CFL flicker with switch off

    I have a house where the CFL's flicker at intermittent times (visible at night in the bedroom ceiling fixture) when the switch is off. The voltage reading at the light socket with the switch in the off position is 63 volts. Has anyone experienced this before and what was the cause. I have checked the house ground and it is fine. Many of the circuits are 12/2 without a ground. I'm wondering if someone tapped off these old circuits with grounded wire and this ground is carrying some voltage. Please let me know what you think?

  2. #2
    Join Date
    Dec 2006
    Location
    Chapel Hill, NC
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    25,963
    Bad switch???? Or is it a dimmer switch???

  3. #3
    Join Date
    May 2007
    Location
    Baton Rouge
    Posts
    770
    Could the switch be a lighted switch?
    Jason

  4. #4
    Join Date
    Jun 2003
    Location
    NE (9.1 miles @5.07 Degrees from Winged Horses)
    Posts
    5,802
    What are you checking voltage to? Get a cord and go all the way back to the service entrance, ensure a grounded connection and take a new voltage reading.

    How close is the house to a high voltage primary?
    Switched neutral? MWBC with intermittent neutral connection?

    Hallucinogens? Torn retina?
    Tom
    TBLO

  5. #5
    Join Date
    Apr 2008
    Location
    Ann Arbor, Michigan
    Posts
    4,566
    091219-0801 EST

    NuVision bulb, 23 W.

    1 megohm series resistor no flash. Insufficient current to overcome leakage in the bulb.

    100k in series. Flash rate about 1/3 Hz.

    10k in series. Flash rate fast. Estimate 3 to 5 per second based on the 100k test.

    Internally there is a rectifier, probably bridge, and a capacitor input filter. Probably there is a voltage level on the capacitor of Vt where below this level little current flows and the capacitor exponentially charges. Then at Vt the voltage is high enough to trigger the driver to the fluorescent tube to cause the capacitor to be discharged. This is somewhat equivalent to an RC oscillator using a neon bulb.

    It appears one can make a useful flashing light with the 10k resistor.

    As suggested a pilot lamp type switch might be the cause.

    .

  6. #6
    Join Date
    Feb 2009
    Location
    Atlanta, GA
    Posts
    277
    We've experienced this with fan remotes and dimmers.

  7. #7
    Join Date
    Jul 2007
    Location
    Iowegia
    Posts
    16,839
    Is it an illuminated switch, or one of those 'no-wiring-needed' RF switches?

  8. #8
    Join Date
    Jun 2009
    Location
    MD
    Posts
    76
    Any chance the circuit is under the control of a X10 device? I've seen that flickering with a plug-in X10 lamp module - they pulse low-voltage when "off" to sense if you have turned the light's switch on-off-on. Its just enough voltage to make CFLs flicker in a dark room. Doesn't sound like this applies here, just throwing out another possible source for the low voltage other than a pilot lamp in the wall switch.

  9. #9
    Join Date
    Apr 2008
    Location
    Ann Arbor, Michigan
    Posts
    4,566
    091221-1714 EST

    With an OAC5 solid-state relay and my previously mentioned NuVision bulb the flash rate is about 0.1 Hz and only the lower half of the tube flashes. Simpson resistance reading, very slight meter movement on the 10k range.

    I checked the leakage resistance on a Crydom D1210 and with a Simpson 270 it was about 8k. However, the flash rate was not as high as I expected and the brightness not as high as when a straight 10k resistor was used.

    Note: the lower current AC X-10s have a Triac output.

    .

  10. #10
    Join Date
    Sep 2005
    Posts
    17

    I'm Stumped by this one

    This one has me stumped. Here's what I know:

    1. replaced 2- 3w switches to the lvrm light, they are not lighted or dimmers. Light still flickers. I have gotten a range of voltage readings from 6v to 69v and the flicker can be seen at 59v. These reading occur with the switches in the off positions. The circuit breaker for this light also has the dnrm light on it and the dnrm CFL doesn't flicker, it's voltage reading is zero.

    2. There are 2 lights upstairs that also flicker, the hall and mst bdrm. These 2 lights are on a different breaker from the lvrm. The voltage readings also fluctuate on these 2 lights. There is another CFL in the second bdrm that is on this same breaker and it has not flickered it's voltage reading is zero.

    3. These voltage reading have been taken inside the fixture sockets and in the wirenuts in the box and they read the same.

    4. I have noticed the 3 lights flicker at different frequencies. The last time I was there the lvrm flickered every 13 sec, hall every 7 sec and mbdrm every 30 sec.

    5. If the breaker is turned off the flickering stops.

    6. I have not been able to determined is this is happening at specific times. I have asked the owners to record when it happens.

    7. There is no x10 or radio frequency devices in this apartment. There are 3 apartments in this building and they each have there own meters and panels.

    As I said, "I'm Stumped", I'm hoping someone can think of something else I can check. Thanks Jan

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